This invention relates generally to heavy duty plastic bags, and more specifically, to a perforation blade used to form an easy-open corner which resists inadvertent bursting during handling of a filled bag. Such bags are commonly used for heavy-duty applications, such as for transport, sale, and storage of materials such as chemicals, salt, fertilizer, lawn lime, potting soil, and the like. The are typically fabricated from LD, HD, or LLD polyolefin sheet or tube stock, such as polyethylene or polypropylene having a thickness in the range of 3 to 12 mils. The sheet or tube stock may be coextruded or monoextruded, and may be a single ply or multi-ply material. The multi-ply material may be multiple thicknesses of the same sheet or tube stock, or different materials to provide particular characteristics, such as strength, flexibility, UV resistance, or color. The sheet stock may also be woven or non-woven synthetic or non-synthetic material. While the invention has particular application to bags with a capacity of from 20 to 100 pounds, the present blade used to form the easy-open corner can be applied to bags of any size.
Conventional, heavy-duty bags of the prior art are typically cut along the top with a knife or other suitable tool to define a sufficiently large opening through which the contents of the bag are dispensed. In the absence of a cutting knife or tool, attempts to manually tear open the bag by hand are often futile, because of the relative thickness and durability of such bags. Once opened, the bag must generally be embraced with both arms, lifted and inverted to dispense the contents from an opening in or near the top of the bag. In many cases, this requires substantial physical effort, and sometimes results in inadvertent uncontrolled dumping or over-dumping of the contents.
In an effort to facilitate opening and control dumping, some heavy duty bags are formed with a perforated, removable corner adapted for being hand-torn to form a pourer. While such bags solve many problems of the prior art, certain disadvantages and limitations remain. Since the perforations formed at the corner of the bag typically pass entirely, or at least partially, through the end seal, the bag is prone to inadvertent rupture and spillage during transport and handling.
Therefore, it is an object of the present invention to provide a perforation blade used to form an improved easy-open corner of a heavy duty bag which resists inadvertent bursting during transport and handling of a filled bag.
It is another object of the invention to provide a bag cutting device which includes an improved perforation blade used to form an easy-open corner.
These and other objects of the present invention are achieved in the preferred embodiments disclosed below by providing a perforation blade used for cutting a perforated tear line in a bag to form an easy-open corner portion. The corner portion is removable to define a pourer through which contents of the bag are dispensed. The bag has first and second walls with joined opposing side edges, opposing end edges, and a seal line proximate one of the end edges for sealing closed an end of the bag. The perforation blade includes a base formed to span the corner portion of the bag. The base has a first end adapted to extend to the end edge of the bag proximate the seal line, and a second end adapted to extend to one side edge of the bag. A series of specifically spaced perforation teeth are formed with the base, and are adapted to penetrate the first and second walls of the bag to form a corresponding series of perforations at the corner portion of the bag. A starter tooth is formed at the first end of the base, and is adapted to cut a starter nick in a skirt of the bag between the end edge and the proximate seal line. A burst protection gap is formed between the starter tooth and a first of the series of perforation teeth. The burst protection gap is adapted for safely receiving the seal line of the bag to prevent severing the seal line when cutting the perforations.
According to another preferred embodiment of the invention, the burst protection gap is at least 50 percent wider than the space formed between the first perforation tooth and a second, adjacent perforation tooth.
According to another preferred embodiment of the invention, the burst protection gap defines a depth at least 20 percent greater than a depth of the space between the first perforation tooth and a second, adjacent perforation tooth.
According to another preferred embodiment of the invention, the starter tooth is larger than the first perforation tooth.
According to another preferred embodiment of the invention, the perforation teeth extend from the burst protection gap to the second end of the base.
According to another preferred embodiment of the invention, the perforation teeth are uniformly spaced to a specific gap dimension.
According to another preferred embodiment of the invention, the perforation teeth have a uniform length.
According to another preferred embodiment of the invention, the base defines a height greater than a length of the first perforation tooth.
According to another preferred embodiment of the invention, the base is formed of spring steel.
In another embodiment, the invention is a bag cutting device with a perforation blade used for cutting a perforated tear line in a bag to form an easy-open corner portion. The perforation blade includes a base formed to span the corner portion of the bag. The base has a first end adapted to extend to the end edge of the bag proximate a seal line, and a second end adapted to extend to one side edge of the bag. A series of closely spaced perforation teeth are formed with the base, and are adapted to penetrate the first and second walls of the bag to form a corresponding series of perforations at the corner portion of the bag. A starter tooth is formed at the first end of the base, and is adapted to cut a starter nick in a skirt of the bag between the end edge and the proximate seal line. A burst protection gap is formed between the starter tooth and a first of the series of perforation teeth. The burst protection gap is adapted for safely receiving the seal line of the bag to prevent severing the seal line when cutting the perforations.
In yet another embodiment, the invention is a method of forming an easy-open corner portion of a bag. The corner portion is removable to define a pourer through which contents of the bag are dispensed. The bag has first and second walls with joined opposing side edges, opposing end edges, and a seal line proximate one of the end edges for sealing closed an end of the bag. The method includes the steps of forming a starter nick in a skirt of the bag between the end edge and the proximate seal line. A series of closely spaced perforations are formed in the first and second walls of the bag. The perforations extend along a predefined tear line from the end edge of the bag proximate the starter nick to one side edge of the bag. When forming the starter nick and perforations, the seal line of the bag is bypassed to avoid severing the seal line during formation of the easy-open corner portion.
According to one preferred embodiment of the method, the easy-open corner portion of the bag is formed using a laser.
According to another preferred embodiment of the method, the easy-open corner portion of the bag is formed using a radiused wheel with outwardly projecting perforation teeth.
According to yet another preferred embodiment of the method, the easy-open corner portion of the bag is formed using an elongated perforation blade.